Low and reverse pressure application hydrodynamic pressurizing seals

ABSTRACT

The present invention relates to circumferential seal ring segments positioned around a rotating shaft so as to prevent fluids from leaking from a lubricant sump during both low and high pressure conditions. The circumferential seal is comprised of a plurality of adjoining annular ring segments facing the rotating shaft. Each sealing ring segment includes a dead end circumferential groove on a shaft-side face of each sealing ring such that, when the segments are joined, the circumferential dead end groove of each segment extends arcuately in the direction of shaft rotation. At least one additional groove is contained on the shaft-side face of each sealing ring segment. Each additional groove may contain a pocket. The additional groove(s) directs and creates pressurized air within the dead end circumferential groove, either directly or indirectly maintaining a seal between the ring segments and the shaft. A bleed hole may also be provided to create a seal between each sealing segment.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of co-pending U.S.Non-Provisional application Ser. No. 12/035,740, filed Feb. 22, 2008,which is a continuation-in-part of U.S. Non-Provisional application Ser.No. 11/821,578, filed Jun. 21, 2007, which claims priority from U.S.Provisional Application No. 60/815,782, filed Jun. 21, 2006. The subjectmatters of the prior applications are incorporated in their entiretyherein by reference thereto.

FEDERALLY SPONSORED RESEARCH AND DEVELOPMENT

None.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an apparatus and method for sealing aliquid sump. More specifically, the present invention relates to sealring segments designed to generate high gas pressures across the sealand around a rotating shaft so as to prevent liquids from leaking from aliquid side of the seal to a gas side of the seal during low and highpressure conditions.

2. Background

There are many applications wherein housings are provided with aplurality of interior sections having rotating parts passingtherethrough, wherein one of the interior housing sections must beisolated from another by means of a seal system. In gas turbineapplications, for example, it is critical that lubricant containedwithin a lubricant chamber of the housing be sealed from an adjacent gasside of the seal. This is especially true along a rotatable shaft whichoften passes from the lubricant side of the seal to the gas side. In anaircraft engine these sump seals are used to separate ambient areas ofhigh pressure air, e.g. the gas side, from an oil wetted area at lowerambient pressures, e.g. the lubricant side. These seals, thereby, servetwo major functions: (1) prevention of oil leakage from the lowerpressure compartment, and (2) minimization of the flow rate of hot airfrom the high pressure area to the oil wetted compartment.

Leakage of liquids from the lubricant side into the gas side adverselyaffects performance of the equipment where the seal is used. In case ofan aircraft engine, oil leakage across the seal into a hot air side maycause oil coking or an engine fire. More specifically, when an oillubricant is used, mixing the oil with the gas could result in formationof oil coke, a byproduct of oil heated to an elevated temperature, whichchemically alters the oil and is detrimental to the gas turbine. Oilcoke can foul seal surfaces reducing the integrity of the seal andprevent proper bearing lubrication within the lubricant sump.Accordingly, it is important in similar applications, not just theaircraft engine, that the lubricant be isolated within a lubricant sumpand that the seal around the rotating shaft not allow the lubricant toescape the sump.

Seals in such applications may comprise either circumferential seals orface-type seals; however, the circumferential shaft seals are the mostwidely used under the above conditions. Circumferential seal is a namedescribing a generic type of seating device used widely, inter alia, onaircraft engine applications. FIGS. 1A and 1B show a liquid side 2 and agas side 3 of a standard circumferential seal assembly 1. FIGS. 2A and2B show back face and bore views of the same standard circumferentialseal ring segment. In each of these figures, the seals consist primarilyof several carbon and/or graphite segments 1 arranged circumferentiallyaround a shaft 5 to form a continuous, relatively stationary sealingring. The segment ends contain overlapping tongue 10 and socket joints15 to restrict leakage at the end gaps of each segment.

Most current circumferential seals utilize a variant of thecircumferential seal illustrated in FIGS. 1 and 2 to address a need forsealing a low pressure liquid compartment from such a high pressure gascompartment. For example, U.S. Pat. No. 5,145,189 discloses a similarcircumferential seal with a shallow groove which redirects pressurizedair to a plurality of deeper vent grooves. U.S. Pat. No. 6,145,843 alsodiscloses a similar circumferential seal with shallow lift pockets influid communication with a high pressure region by a plenum chamber.Both of these solutions rely completely on the high pressuredifferential between the lubricant side and the gas side to achieve eachrespective sealing function. To this end, in low gas pressureconditions, anywhere from 5 psi and below and including negativepressures, these known circumferential seals can weep, namely, leakliquids from the liquid side into the gas side. Liquid leaking, as notedabove, increases the risk of oil coking and fouling the seal face. Thisincreases the risk of engine fire and increases the risk of oil odorwithin a vehicle housing the engine.

Accordingly, a seal is desired which may function to prevent liquid oroil leaking from a liquid or oil side to a gas side of an application,such as a turbine engine, wherein the seal may prevent leaking under lowpressure differentials between a lubricant side and a gas side, as wellas, high pressure differentials. The present invention, as disclosedherein, addresses this need.

SUMMARY OF THE INVENTION

The present invention relates to an apparatus and method for sealing aliquid sump. More specifically, the present invention relates tocircumferential seal ring segments designed to generate high gaspressures across the seal face and around a rotating shaft so as toprevent liquid from leaking from a lubricant side to a gas side of theseal during both low and high pressure conditions.

The present invention includes a circumferential seal within an annularseal assembly, which is adapted to be received by an annular sumphousing. More specifically, the annular sump housing substantiallysurrounds a rotatable shaft forming a sump chamber wherein the shaftpasses through the chamber and through at least one open end of the sumphousing. A fluid seal assembly is adapted to be received by the open endof the sump housing through which the shaft passes, and is comprised ofan annular seal housing with an annular flange at one end and a windbackat an opposing end. The fluid seal assembly is coupled to the open endof the sump housing by the annular flange such that the fluid sealhousing and windback are held within the open end on an interior side ofthe sump chamber and surrounds the shaft so as to form a seal cavitytherebetween. In this preferred configuration, the interior side of thesump chamber is the lubricant side of the sump and the exterior side ofthe chamber is the gas side.

The seal cavity formed between the shaft and fluid seal housing is sizedto receive the circumferential seal of the present invention, which iscomprised of a plurality of segmented rings mechanically urged inwardlytoward the shaft. The seal may also be biased against a seal cavity wallby a plurality of springs and support rings. By urging the seal againstboth the shaft and the seal cavity wall, the seal and, ultimately, thefluid seal assembly isolate the sump housing chamber such that lubricantmay be prevented from passing through the open end of the housing sump,i.e. from the lubricant side to the gas side, when the shaft is notrotating.

The circumferential seal of the present invention is comprised of aplurality of adjoining annularly sealing ring segments facing therotating shaft wherein each sealing ring segment includes a dead endcircumferential groove adjoined with a bore dam and at least oneadditional groove machined within a shaft-side face of each sealing ringsegment. Specifically, the circumferential dead end groove and bore damare at a position on the shaft-side face closer to the liquid regionthan to the gas region wherein the bore dam is exposed to the liquidregion and is spaced between the liquid region and the dead end groove.When the segments are positioned proximate the shaft surface, thecircumferential dead end groove of each segment extends arcuately in thedirection of shaft rotation.

At least one additional groove is contained on the shaft-side face ofeach sealing ring segment in fluid communication with the dead endgroove. The additional groove(s) is designed to direct fluid flow intothe dead end circumferential groove such that fluid directed into thedead end annular groove increases fluid pressure within the dead endcircumferential groove, thereby, forming a seal between the sealsegments and the shaft. These additional groove(s) may be comprised ofone or more hydrodynamic inclined grooves, hydrodynamic pockets (with aninlet and an outlet), axial bore grooves, or similar embodiments ofstructures, as defined herein.

In one embodiment, the additional groove is one or more hydrodynamicinclined pumping grooves. These hydrodynamic inclined pumping groovesextend from the dead end groove at an oblique pitch angle relative tothe longitudinal axis of the ring seal segment so as to be in concertwith the direction of rotation of the rotating shaft. The hydrodynamicpumping groove(s) may be of a constant width, variable width, constantdepth, or variable depth. In a non-limiting example, the width and/ordepth of the hydrodynamic groove(s) may be greater at a groove mouththan at a position of communication with the dead end groove. In anotherembodiment, a segment comprising more than one hydrodynamic groove mayprovide a unique depth and/or width of each groove, relative to theother inclined grooves of each seal segment.

In operation, when the shaft rotates, the inclined grooves direct fluid,preferably air, generated by the rotation of the shaft along theinclined grooves and into the dead end groove. As the air passes alongthe inclined grooves, it begins to accumulate within the dead endcircumferential groove, thus increasing the pressure therein. Thispressure is redirected toward the shaft creating a lift force on theseal segments wherein the lift force expands the sealing segments awayfrom the shaft creating a minute clearance between the shaft-face of theseal segments and the rotating shaft. The redirection of the pressurizedair within the dead end groove toward the shaft also creates anair/pressure seal within this minute clearance wherein the force of thehigh-pressure gas is at a sufficient velocity to prevent lubricantstored within the chamber from passing through the clearance. This airpressure seal is juxtaposed to the bore dam of the shaft-face of theseal such that the bore dam acts in concert with the air/seal to preventlubricant from escaping from the housing chamber during operation of theturbine engine. In other words, lubricant is prevented from escapingfrom the lubricant side to the gas side of the chamber. Thisconfiguration has the advantages of creating an air seal that does notinterfere with the rotation of the shaft, while reducing the wear on theshaft-side face seal as a result of the rotation of the shaft.

Pressurized gas from the dead end circumferential groove may also bereleased into the tongue/socket joints by way of a gas bleed hole. Byallowing pressurized air from the dead end groove to leak into thesockets, the pressurized air also acts as a seal within thesocket/tongue joints of two adjacent seal segments and flows at a highvelocity so as to prevent lubricant from the liquid side from passingthrough the joints of the seal segments. To this end, this preventsliquid weepage through the tongue/socket joints.

In a second embodiment, the additional groove(s) is comprised of ahydrodynamic shallow pocket wherein the hydrodynamic shallow pocket isin fluid communication with the dead end circumferential groove by wayof an outlet and fluid flow enters the pocket by way of an inlet. Thepocket, inlet and outlet may be of a constant depth, a variable depth, aconstant width, or a variable width. In a non-limiting example, depthand/or width the pockets may be greater proximate to the inlet than atthe outlet. In a further example, the inlet and outlets may be at anoblique angle, relative to the longitudinal axis of the ring segments,such that the groove is in concert with the direction of rotation of theshaft. In an even further embodiment, a dam, with an optional bleedslot, may be present between each pocket and its respective outletgroove. The dam functions to increase pressure build up such that airflow is forced over the dam, or through the bleed slot, therebyincreasing the air pressure within the dead end groove. In a furtherembodiment, a bleed slot may also be present between the dead end grooveand the socket such that a seat is created at the socket/tongue joint inaccordance with the above.

In operation, when the shaft rotates, the shallow pockets direct airgenerated by the rotation of the shaft along the inlet through theshallow pocket and the outlet to, ultimately, the dead endcircumferential groove. As air passes along the shallow pocket, it ispressurized and begins to accumulate within the dead end circumferentialgroove, thus generating high pressure therein. This high pressure withinthe dead end circumferential groove creates a lift force on the sealsegments and forms a seal around the rotating shaft in accordance withthe above.

In a third embodiment, the additional groove(s) is comprised of an axialbore groove in fluid communication with the dead end circumferentialgroove. The axial bore groove may be in direct fluid communication withthe dead end circumferential groove, or alternatively, the axial boregroove may be in fluid communication with the dead end circumferentialgroove by way of at least one longitudinal bore groove and a pressurechamber. The longitudinal bore groove(s) extends from the axial grooveand along the longitudinal axis of the ring seal segment to a pressurechamber wherein the pressure chamber is in direct fluid communicationwith the dead end circumferential groove. Each longitudinal boregroove(s) may contain one or more hydrodynamic grooves on its innersurface wherein the hydrodynamic groove(s) extends along thelongitudinal bore groove at an oblique angle with respect to thelongitudinal axis of the longitudinal bore groove. In one embodiment,the hydrodynamic groove(s) is angled such that it facilitates thedirection of air from the axial groove into the pressure chamber. Thepressure chamber and/or axial groove may further comprise a dam,optionally with a bleed slot, between the pressure chamber and the deadend circumferential groove. The dam functions to increase pressure buildup such that air flow is forced over the dam, or through the bleed slotinto the dead end groove, thereby, increasing the air pressure withinthe dead end groove. The pressure chamber may also include a radialbleed slot placing the pressure chamber, or axial groove, and the socketinto fluid communication.

Alternatively, at least two longitudinal bore grooves may extend fromthe axial bore wherein the first longitudinal bore groove extends to afirst pressure chamber and the second longitudinal bore groove extendsto a second pressure chamber. The first pressure chamber is in fluidcommunication with the dead end circumferential groove in accordancewith the above. The second pressure chamber is only in fluidcommunication with the socket, by way of the radial bleed valve.

In operation, when the shaft rotates, the axial bore groove(s) directsair generated by the rotation of the shaft into the dead endcircumferential groove either directly or by way of one or morelongitudinal bores grooves and pressure chambers. As air passes alongthe axial bore groove or the longitudinal bore grooves, it begins toaccumulate within the dead end circumferential groove, thus generatinghigh pressure therein. The high pressure within the dead end groovecreates a seal in accordance with the above. Additionally, pressure maybleed into the socket by way of the bleed valve, thereby creating a sealin the tongue/socket joint.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B are a partially broken elevation taken in section, withsection lines omitted for drawing clarity, of liquid and gas sides of aprior art circumferential seal assembly.

FIGS. 2A and 2B are an elevation of an axially facing surface and a viewof a radially inwardly facing surface of a prior art circumferentialseal ring segment forming a part of the assembly shown in FIG. 1.

FIGS. 3A and 3B are a partially broken elevation taken in section, withsection lines omitted for drawing clarity, of liquid and gas sides of acircumferential seal assembly of the present invention.

FIGS. 4A and 4B are an elevation of an axially facing surface and a viewof a radially inwardly facing surface of a circumferential seal ringsegment including inclined pumping grooves in accordance with theinvention.

FIGS. 5A and 5B are an inboard view of one segment of the sealing ring,with an inclined pumping groove, with the direction of the pumpinggrooves in accordance with the direction of shaft rotation so as tofacilitate pumping provided by the grooves.

FIG. 6 illustrates two adjacent circumferential seal segments havinginclined pumping grooves in accordance with the invention with a highpressure gas release hole being provided from the dead end arcuategroove of one of the segments through a socket face into the jointbetween the adjacent segments.

FIG. 7 is similar to FIG. 6 but illustrates another embodiment of thegas release slot, in place of the gas release hole, whereby highpressure gas may be released from the circumferential groove through thesocket face into tongue and groove the joint between two adjacentcircumferential seal segments having inclined pumping grooves.

FIG. 8A-8E illustrates a number of variations of inclined pumpinggrooves in accordance with the invention, with each variation beingshown on a single circumferential seal segment.

FIGS. 9A and 9B illustrates a shallow pocket hydrodynamic seal ringsegment showing at the top of the figure a view of the segment taken inthe axial direction and at the lower portion of the figure a view of thesegment taken looking at a radially outwardly direction, showing thepockets located in the radially inwardly facing surface of the sealsegment.

FIG. 10A-10E illustrates various forms of pockets useful in a shallowpocket seal of the type illustrated in FIG. 9. Specifically, FIG. 10Aillustrates a constant depth pocket; FIG. 10B illustrates a pocket witha taper having higher depth at the inlet end and lower depth at theoutlet end; FIG. 10C illustrates a pocket having a very small dambetween the end of the pocket and the outlet groove; FIG. 10Dillustrates a pocket with a bleed slot to release generated highpressure directly into the outlet groove; FIG. 10E illustrates angularorientation of the inlet and outlet grooves for the pocket to improvegas flow into the shallow pocket and release generated high pressure gasfrom the pocket into the dead end annular groove of the circumferentialseal segment.

FIG. 11 is a view, looking radially outwardly, of the radially inwardlyfacing surface of a circumferential seal segment having a single annularhydrodynamic groove connected to a socket bleed hole, all in accordancewith the invention.

FIG. 12 is a view similar to FIG. 11 where the circumferential sealsegment has two annular hydrodynamic grooves, one annular hydrodynamicgroove being connected to a socket bleed hole and a second annularhydrodynamic groove being connected to the circumferential bore groove.

FIG. 13 is a view similar to FIGS. 11 and 12 where the circumferentialseal segment has three annular hydrodynamic grooves connected to thecircumferential bore groove and has an optional socket bleed hole.

FIG. 14 is a view similar to FIGS. 11, 12 and 13 of a circumferentialseal segment where the segment shown in FIG. 14 has two sets of threeannular hydrodynamic grooves connected to the circumferential boregroove with an optional socket bleed hole.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to an apparatus and method for sealing aliquid sump. More specifically, the present invention relates tocircumferential seal ring segments designed to generate high gaspressures across the seal face and around a rotating shaft so as toprevent fluids from leaking from a lubricant sump during both low andhigh pressure conditions. The circumferential seal is part of a largerseal assembly that is adapted to fit within a sump housing, as describedherein. The circumferential seal is comprised of a plurality ofadjoining annularly sealing ring segments facing the rotating shaftwherein each sealing ring segment includes a dead end circumferentialgroove adjoined with a bore dam and at least one additional groovemachined within a shaft-side face of each sealing ring segment.Specifically, the circumferential dead end groove and bore dam are at aposition on the shaft-side face closer to the liquid region than to thegas region where the bore dam is exposed to the liquid region and isspaced between the liquid region and the dead end groove. When thesegments are positioned proximate the shaft surface, the circumferentialdead end groove of each segment extends arcuately in the direction ofshaft rotation.

At least one additional groove is contained on the shaft-side face ofeach sealing ring segment wherein the additional groove(s) directs fluidflow into the dead end circumferential groove such that fluid directedinto the dead end annular groove increases air pressure within the deadend circumferential groove. As discussed further herein, thispressurized air forms a seal between the seal segments and the shaft.The additional groove(s) may be comprised of one or more hydrodynamicinclined grooves, hydrodynamic pockets (with an inlet and an outlet),axial bore grooves, or the like, as defined herein.

Referring to FIGS. 3A and B, a fluid seal assembly 20 is illustrated.The fluid seal assembly 20 is comprised of an annular fluid seal housing25 flanked by a flange 30 at a first end and a windback 35 at anopposing second end. The annular fluid seal housing 25 is adapted toreceive and sealingly engage a rotatable shaft 40, as discussed below.Extending from one end of the fluid seal housing 25 is an annular flange30. The flange 30 extends radially from the fluid seal housing 25 and isadapted to substantially surround the shaft 40. The flange 30 is alsoadapted to be secured to a housing of the lubricant sump (notillustrated) such that the fluid seal assembly 20 isolates a lubricantchamber (represented generally by reference 21) from a gas side(represented generally by reference 22) of the assembly. Specifically,the flange 30 may be coupled to the sump by a plurality of bolts passingthrough a plurality of holes of the flange 30 and threadingly engaging aplurality of recesses of the sump housing (not illustrated). However,the invention is not limited to this embodiment and the flange 30 may becoupled to the sump by a screw, clasp, strap, or any other meansunderstood in the art to secure the flange to a housing. Moreover, theinvention is not limited to a plurality of recesses within the housing.Rather, the sump may also comprise a hook, screw, bolt or the likeextending therefrom wherein the hook, screw, bolt, etc. is adapted topass through the holes in the flange 30. An external means such as anut, clasp, strap, retention ring, or the like may then be utilized tofurther secure the flange 30 to the sump. Regardless of the type ofsecuring mechanism, the action of securing the flange 30 to the sumpfunctions to secure the fluid seal assembly 20 to the sump housing.

The fluid seal housing 25 may also contain an O-ring (not illustrated),or other similar sealing mechanism, within a groove or recess 45 of thefluid seal housing 25. The O-ring is inserted into the groove 45 suchthat, when the fluid seal assembly 20 is secured to the sump housing (byway of the flange), the O-ring sealingly engages sump housing. Thissealing engagement prevents leakage of the lubricant from the lubricantsump through the space between the fluid seal housing 25 and sumphousing.

The annular fluid seal housing 25 is configured such that a bore passestherethrough wherein the bore opens to an annular seal cavity 50. Theseal cavity 50 is adapted to receive the seal of the present inventionand is sized to allow the shaft 40 to pass therethrough. Moreparticularly, the seal cavity 50, along with the fluid seal housing 25,extends radially around the shaft 40 with a plurality of radial steppedseal-receiving grooves 55 an end of the seal cavity 50 proximal to theflange 30. The sealing cavity 50 and seal-receiving grooves 55 extendco-axially with the fluid seal housing 25 such that the seal cavity 50and stepped seal-receiving grooves 55 substantially surround the shaft40. The resulting diameter of the seal cavity 50 may be of any diameterunderstood in the art to support a circumferential seal and, ultimately,to seat the lubricant sump.

A plurality of circumferential seal segments 60 are adapted to fitwithin the seal cavity 50 such that the resulting seal is held in placeby both a cavity wall and rings secured within the steppedseal-receiving grooves 55. More specifically, the seal segments 60 mayfit within the seal cavity such that they substantially surround theshaft 40 and isolate the fluid within the sump. To this end, referringto FIG. 4, each seal segment may contain a tongue 65 at one end of thesegment and a socket 70 at the opposing end such that the socket 70 ofone seal segment is adapted to receive the tongue 65 of an adjacentsegment such that the seal segments fit together around thecircumference of the entire shaft 40. The seal segments 60 may be formedfrom carbon or carbon-graphite or any material understood in the art fora sealing surface within a chamber and along a runner or shaft. The sealsegments, when joined, may form a ring with an outer diameter slightlysmaller than the diameter of the seal cavity 50 and an inner diameterapproximately the same diameter as the shaft 40. The number of sealsegments 60 required to form the ring substantially around the shaft 5varies with the size of the shaft. In other words, larger shafts mayrequire a greater number of seal segments.

Referring again to FIG. 3, along the outer diameter of each seal is arecess 75 wherein, when the seal segments are joined, a continuousrecess is formed about the seal segments 60. The recess 75 is adapted toreceive a device that mechanically urges the seal segments against theshaft 40. In a non-limiting example, the device may be comprised of acircular coil spring 80 wherein the spring serves to urge the sealsegments against the shaft 40, while still allowing the segments toexpand or contract with the pressure differential created by the shaftrotation, as discussed below. As such, when the shaft 40 is not inoperation, the action of the coil spring 80 on the shaft 40 creates aseal on the surface of the shaft that prevents lubricant from passingbetween the shaft and seal segments. The present invention, however, isnot limited to a coil spring and may be comprised of any deviceunderstood in the art to bias or urge seal segments against a shaft 40.

Isolating and sealing the lubricant sump is further enhanced by biasingthe seal ring segments 60 against a seal cavity wall 85. Specifically, aseal support ring 90 may be positioned within the seal cavity 50 to biasthe seal segments against the cavity wall 85, wherein the seal supportring 90 is fixed in position by one of the stepped seal-receivinggrooves 55. The seal support ring 90 may be further fixed by a retainingring 95, desirably a split retaining ring, which is received withinanother of the stepped seal-receiving grooves 55. As illustrated inFIGS. 3A and 3B, it is desirable that the seal support ring 90 and theretaining ring 95 are secured within adjacent stepped seal-receivinggrooves 55 such that the retaining ring 95 biases the seal support ring90 toward the seal ring segments 60 and the interior of the seal cavity50.

In one embodiment, the seal support ring 90 mechanically urges the sealring segments 60 against a seat cavity wall 85 through a plurality ofsprings. For example, the seal 60 may be urged toward the seal cavitywall 85 by a series of compression springs 100. Each compression spring100 may extend from a series of pockets or a long continuous groovealong the seal ring segments 60 to, ultimately, contact the seal supportring 90. The fixed position of the seal support ring 90 and theretaining ring 95 within the stepped seal-receiving grooves 55 allowsthese elements to urge the seal 60 against the seal cavity wall 85 byway of the action of the series of springs 100 retained therebetween.The present invention is not limited in the number of springs utilized;however, it is desirable that a sufficient number of springs be utilizedto evenly compress the seal ring segments 60 against the seal cavitywall 85 without hindering the ultimate function of the sealing segments60, i.e. to isolate the lubricant sump from the gas side.

The seal ring segments 60 are specifically machined to contain aplurality of grooves along a shaft-side face of the each segment suchthat these grooves generate high gas pressures across seal rings and theshaft. This increased pressure prevents fluid from leaking within spacesbetween the shaft 40 and the seal segments 60 during the operation ofthe shaft 40. In a first embodiment the grooves along the shaft-sideface 110 of the seal segments 60 are a dead end circumferential groove115 and at least one or a plurality hydrodynamic inclined pumpinggrooves 105. The circumferential dead end groove of each segment extendsalong the longitudinal axis of the shaft-face of the ring segment 60such that, when the segments are linked, the dead end circumferentialgroove extends arcuately in the direction of shaft rotation. Preferably,a bore dam is spaced between the dead end circumferential groove and thelubricant side of the chamber. The width and depth of the grooves 115and 105 are dependent upon multiple factors including, but not limitedto, the engine application, shaft rotational speeds, desired seat lifeand the like. In one embodiment, the dead end circumferential groove 115is machined at a position proximal to the bore dam 116 and the liquidside of the seal and is within the range of 0.040 to 0.060 inches indepth and within the range of 0.040 to 0.070 in width.

Referring to FIGS. 4A and 4B, the bore configuration of the inclinedpumping groove seal ring segment is illustrated in accordance with thepresent invention. Specifically, a plurality of shallow inclined groovesis illustrated on the bore or shaft-side face of the seal ring segments60. Each inclined groove extends across the face of the seal at anoblique angle relative to the longitudinal axis of the segment. Eachinclined groove connects to and is in fluid communication with a deadend circumferential groove 115 running along the shaft-side face 110 ofthe seal segment 60.

Referring to FIGS. 8A-C, various forms of inclined pumping grooves areillustrated in accordance with the present invention. Specifically,these inclined pumping grooves can have either sharp corners or crosssections with radii. Depending on the application, the number ofgrooves, groove depth, and groove width can be adjusted. As noted above,the width, depth, and positing of the inclined pumping grooves 105 aredependent upon multiple factors including, but not limited to, theengine application, shaft rotational speeds, desired seal life and thelike. In one embodiment, the hydrodynamic inclined grooves may be withinthe range of 0.0005 to 0.035 inches in depth and 0.040 to 0.093 inchesin width. In a further embodiment, it is desirable that the hydrodynamicinclined grooves be within a range of 0.020 to 0.025 inches in depth and0.076 to 0.093 inches in width. To this end, each groove may becomprised of a constant width, constant depth, variable width, and/or avariable depth. In a non-limiting example, as illustrated in FIG. 8C,the inclined groove may have a depth and/or width that is greater at anend of the groove distal to the dead end groove 115 than at an end ofthe groove proximal and/or in communication with the dead end groove115, thereby increasing the air pressure as the air flow approaches thedead end groove 115. In an additional non-limiting embodiment, if theseal segment is comprised of more than one hydrodynamic inclined groove,each groove may be of a unique width and/or depth relative to the othergrooves, thereby creating variable pressures among the grooves thatallow the seal to continually pressurize the air flow under varyingcircumstances. Each segment may also have grooves with multiple depths(multi-depth grooves), as illustrated in FIGS. 8D and 8E, instead of thesame depths. The advantage of having segments with multi-depth groovesis that in the event the very shallow groove(s) wears to the point ofbeing ineffective due to rubbing wear, the other grooves will pump thegas and generate high pressures until they wear down and even wear offone at a time.

The depth, width and pitch angle of the inclined grooves 105 and thedepth and width of the dead end circumferential groove 115 may also bebased on the particular application of the seal. Specifically, thesemeasurements may be tailored based on factors such as the speed ofrotation of the shaft 40, pressure differential between the sump and thegas side of the seal, temperature, or similar parameters to optimize theefficiency of air movement and the pressure created with in the dead endcircumferential groove. In one embodiment, the dimensions of the deadend groove 115 and the inclined grooves 105 are such that the pressuregenerated within the dead end groove 115 is higher than the pressure onthe gas side 22 of the seal.

As indicated above, and illustrated in FIGS. 5A and 5B, the directionalorientation and pitch angle of the inclined pumping grooves 105 isdependant upon the direction of rotation of the shaft. Properorientation of the inclined pumping grooves 105, relative to thedirection of shaft rotation, must be in concert with the direction ofthe sheer forces generated by the shaft rotation. The inclined pumpinggrooves 105 may, therefore, employ either a right hand pitch thread (asillustrated in FIG. 5B) or a left hand pitch thread (as illustrated inFIG. 5A). For a shaft rotating clockwise, a pitch angle of the threadwould be a right hand thread (FIG. 5B), such that the grooves are inconcert with the sheer forces or fluid flow generated by right-handedrotation. Conversely, for counterclockwise rotation of the shaft, thepitch angle of the thread would be the opposite to achieve the sameresult. The orientation of the tongue 65 and the socket 70 are alsodependant upon the rotation of the shaft. For example, when orientingthe inclined pumping groove direction in a left hand thread, thelocations of the tongue and sockets of the segments also reversed, ascompared to a right hand thread.

The angle of the inclined pumping grooves 105, relative to thelongitudinal axis of the seal segment, 60, is dependent upon a myriad offactors including, but not limited to, the number of seal segments 60required to substantially surround the shaft 5, the length of each sealsegment 60, the number of inclined grooves in the seal segment, thelength of each inclined groove, the engine application and shaft speeds,and the like. Specifically, the inclined pumping grooves 105 may bebetween 3 degrees and 45 degrees, relative to the longitudinal axis ofthe seal segment 60. For example, in one non-limiting embodiment aplurality of test seals forming a 8.700 inch diameter contains oneinclined pumping groove 105 with an angle of 4.5 degrees, relative tolongitudinal axis of the seal segments. In another non-limitingembodiment a plurality of test seals forming a 8.700 inch diametercontains three inclined pumping grooves 105 each at an angle of 10.0degrees, relative to the longitudinal axis of the seal segments.Accordingly, the pitch angle is not static across all embodiments of theseal segments and may be changed based upon the above parameters.

In addition to a dead end circumferential groove and at least oneinclined groove, the present embodiment may also contain a bleed hole120. Referring to FIGS. 6 and 7, a high-pressure gas bleed hole 120 isillustrated as extending between the socket 70 and the dead endcircumferential groove 115. Specifically, the gas bleed hole 120 extendsfrom the dead end circumferential groove 115 to a point within a jointsegment 125 where a tongue 65 of one seal segment 60 meets the socket 70of a second seal segment 60. To this end, the bleed hole 120 places thesocket 70 into fluid communication with the dead end circumferentialgroove 115.

In operation, when the shaft is not rotating, the coil spring 80 urgesthe seal segments toward the stationary shaft 40 and creates a sealbetween the shaft and housing 20. As the shaft begins to rotate, theinclined grooves 105 direct air generated by the rotation of the shaft40 into the dead end groove 115. Air begins to accumulate within theinclined grooves and the dead end circumferential groove 115, thusgenerating high pressure therein. This high pressure may be higher thanthe pressure exerted on the seal segments 60 from a gas side 22 of theseal. In either case, the pressure within the dead end groove 115 isredirected toward the shaft creating a lift force on the seal segmentswherein the lift force expands the sealing segments away from the shaftcreating a minute clearance between the shaft-face of the seal segmentsand the rotating shaft. The redirection of the pressurized air withinthe dead end groove toward the shaft also creates an air/pressure sealwithin this minute clearance wherein the force of the high-pressure gasis at a sufficient velocity to prevent lubricant stored within thechamber from passing through the clearance. This air pressure seal isjuxtaposed to the bore dam of the shaft-face of the seal such that thebore dam acts in concert with the air/seal to prevent lubricant fromescaping from the housing chamber during operation of the turbineengine. In other words, lubricant is prevented from escaping from thelubricant side to the gas side of the chamber. This configuration hasthe advantages of creating an air seal that does not interfere with therotation of the shaft, while reducing the wear on the shaft-side faceseal as a result of the rotation of the shaft.

Additionally, pressurized gas from the dead end circumferential groove115 may be released into the joints 125 by way of the gas bleed hole120. By providing a bleed hole 120 connecting the dead endcircumferential groove 115 and the socket 70 gas pressure built upwithin the dead end circumferential groove continues to escape into thejoints even at low or reverse pressure conditions. This pressurized airacts as a seal within the socket/tongue joints of two adjacent sealsegments and prevents liquid webpage therethrough.

The above embodiment of the present invention is advantageous becausethe inclined grooves greatly reduce leakage of liquids into the regionon the gas side of the seal. Specifically, the redirection of air intothe dead end groove 115, across the seal face, and seal segment joints125 function to increase pressure within these grooves and joints.Because the dead end groove 115 is on the shaft-side face 110 of theseal, the pressure within the dead end groove 115 creates anair/pressure seal around the rotating shaft and lifts the seal segmentsoff of the shaft such that the segments do not interfere with therotation of the shaft. Accordingly, the seal between the lubricant sideand gas side is maintained regardless of the pressure differentialbetween the gas side and liquid side of the seal. The seal is able tofunction during both high and low air side to oil side pressuredifferential, as well as when negative pressure exists on the air side.

The present invention is also advantageous, as compared to abore-rubbing circumferential seals, because the hydrodynamic sealsaccording to the invention, when running on a film of gas, generate lessheat due to friction. Less heat generation means less cooling oil isneeded. As the seal runs on a thin film of gas, there is no rubbingbetween the seal bore and the runner or the shaft because there isessentially no contact. Hence, there is no significant seal bore wear.This provides extended seal wear life compared to a standardcircumferential seal contacting the runner.

Finally, the present invention is advantageous because is allowsvariability with the width of the bore dam 116. Specifically, in priorseals a smaller bore dam was more efficiency for the reduction of boreloading and heat generation during rotation of the shaft. However, asmaller bore dam prevents the use of a more robust type of seal. In thepresent invention, the additional grooves, e.g. hydrodynamic grooves,provide for reduced bore loading. Accordingly, the size of the bore dam116 may be varied with the present invention so as to form a more robustseal face.

In a second embodiment of the present invention, referring to FIGS. 9Aand B, the additional grooves along the shaft-side face 110 of the seal60 are formed by at least one hydrodynamic shallow pocket 129, comprisedof a pocket 130, inlet 135 and outlet 140, and a dead endcircumferential groove 115. Specifically, the pockets 130 may besubstantially square shaped, as illustrated. However, the pocket is notlimited to this configuration. Rather, the pocket 130 may berectangular, circular, oval, or any other aerodynamic and/orhydrodynamic configuration understood in the art. Extending from one endof each pocket 130 which is distal to the dead end circumferentialgroove is an inlet 135 wherein the inlet 135 extends from the pocket 130such that it is adapted to receive fluid flow from the rotatable shaft,as discussed below. Extending from an opposing end of each pocket 130,which is proximal to the dead end circumferential groove 115, is anoutlet 140 wherein the outlet 140 places each pocket 130 into fluidcommunication with the dead end circumferential groove 115.

As with the first embodiment, the second embodiment may also include ableed hole 120. The bleed hole 120 may be at one end of the dead endcircumferential groove 115 may place the dead end circumferential groove115 into fluid communication with the socket 70. These holes and/orslots are in accordance with the above and are the same as shown in FIG.6 and in FIG. 7.

The dimensions of the hydrodynamic shallow pockets 129 are not limitedto one embodiment. FIG. 10 shows various forms of shallow pockets, allin accordance with the present invention. Specifically, the number ofpockets, the depth, the width, and the length can be machined, asneeded, based upon the particular application of the seal assembly. Thewidth and depth of the pockets 130, outlets 140 and inlets 135 aredependent upon multiple factors including, but not limited to, theengine applications shaft rotational speeds, desired seal life and thelike. In one embodiment, the hydrodynamic shallow pocket may be withinthe range of 0.0005 to 0.035 inches in depth and 0.040 to 0.093 inchesin width. In a further embodiment, it is desirable that the hydrodynamicshallow pockets be within a range of 0.020 to 0.025 inches in depth and0.076 to 0.093 inches in width. The inlet 135 and outlet 140 may be aconstant depth and/or width and the pocket 130 may be the same orslightly larger width and/or depth. In another embodiment, asillustrated in FIG. 10B the shallow pocket 130 may be tapered, with agreater depth and/or width proximal to the inlet 135 and a smaller depthand/or width proximal to the outlet 140, thereby increasing the airpressure as the air flow approaches the dead end groove 115. In afurther embodiment, as illustrated in FIG. 10C the shallow pocket 130may be of an even or tapered depth with a dam 145 between the pocket 130and the outlet 140. This arrangement generates very high pressure withinthe pocket 130. Specifically, the generated pressure builds up and isforced over the dam 145 into the outlet 140. This, in turn, supplieshigh pressure into the dead end circumferential groove 115. In anotherembodiment, referring to FIG. 10D, a bleed slot 150 may be added throughthe dam 145 to release the generated high pressure directly into theoutlet 140.

Depending on the application, each seal segment 60 may even have shallowpockets 130 with various depths (multi-depth pockets), instead of allpockets being the same depth. The advantage of having segments withmulti-depth pockets is that in the event the very shallow pocket wearsdown or even off due to rubbing wear, the other pockets will pump thegas and generate high pressures until they wear down or even wear off,one at a time. To this end, these multi-depth pockets may be inaccordance with the above and in accordance with FIGS. 5D and 8E.

Depending on the application, the inlet 135 and the outlet 140 may beangled, as shown in FIG. 10E, preferably, such that the angle of theinlet 135 and outlet 140 is in concert with the direction of shaftrotation. The inlets 135 and outlets 140 of the shallow pocket 129 may,therefore, employ either a right hand pitch angle (not illustrated) or aleft hand pitch angle (FIG. 10E) depending upon the direction ofrotation of the shaft. For a shaft rotating clockwise, a pitch angle ofthe thread would be a right hand angle (not illustrated), thus pushingthe air toward the dead end groove 115. Conversely, for counterclockwiserotation of the shaft, the pitch angle of the thread would be a lefthand thread (FIG. 10E) to achieve the same result.

In each of the above embodiments, the varying measurements may befurther tailored based on factors such as the speed of rotation of theshaft 40, pressure differential between the sump and the gas side of theseal, temperature, size of the rotatable shaft, or similar parameters tooptimize the efficiency of air movement and the pressure created with inthe dead end circumferential groove. In one embodiment, the dimensionsof the dead end groove 115 and the shallow pockets 130 are preferablysuch that the pressure generated within the dead end groove 115 ishigher than the pressure on the gas side 22 of the seal. To this end,the measurements of each of the above elements may be scaled up or downbased upon the size of the fluid seal assembly and the aforementionedfactors in tailoring the measurements thereof.

The seal ring segments are coupled, as discussed above, about thecircumference of a rotatable shaft by way of the tongue and sockets andare biased against the shaft surface when the shaft is non-operational.When the shaft rotates, the hydrodynamic shallow pockets 129 direct airgenerated by the rotation of the shaft 40 along the inlet 135 throughthe pocket 130 and the outlet 140 to, ultimately, the dead endcircumferential groove 115. As air passes along the hydrodynamic shallowpocket 129, it begins to accumulate within the dead end circumferentialgroove 115, thus generating high pressure therein. In one embodiment,the high pressure generated within the dead end groove 115 may be higherthan the pressure exerted on the seal segments 60 from a gas side 22 ofthe seal. In either case, the pressure within the dead end groove 115 isredirected toward the shaft creating a lift force on the seal segmentswherein the lift force expands the sealing segments away from the shaftcreating a minute clearance between the shaft-face of the seal segmentsand the rotating shaft. The redirection of the pressurized air withinthe dead end groove toward the shaft also creates an air/pressure sealwithin this minute clearance wherein the force of the high-pressure gasis at a sufficient velocity to prevent lubricant stored within thechamber from passing through the clearance. This air pressure seal isjuxtaposed to the bore dam of the shaft-face of the seal such that thebore dam acts in concert with the air/seal to prevent lubricant fromescaping from the housing chamber during operation of the turbineengine. In other words, lubricant is prevented from escaping from thelubricant side to the gas side of the chamber. This configuration hasthe advantages of creating an air seal that does not interfere with therotation of the shaft, while reducing the wear on the shaft-side faceseal as a result of the rotation of the shaft.

The second embodiment of the present invention containing thehydrodynamic shallow pockets has the same advantages as the firstembodiment. Specifically, the hydrodynamic shallow pockets areadvantageous because they greatly reduce leakage of liquids into theregion on the gas side of the seal, regardless of the pressuredifferential across the face of the seal. In other words, the seal isable to function during both high and low air side to oil side pressuredifferential, as well as when negative pressure exists on the air side.Furthermore, the hydrodynamic shallow pockets generate less heat due tofriction because there is minimal rubbing between the seal bore and therunner or the shaft. This provides extended seal wear life compared to astandard circumferential seal contacting the runner. Finally, thehydrodynamic shallow pockets is advantageous because it provides forreduced bore loading, thus, allowing for a more robust seal face.

In a third embodiment of the present invention, referring to FIG. 11,the additional grooves along the shaft-side face of the seal 60 is atleast one axial bore groove 155, which extends perpendicularly to thelongitudinal axis of the seal segment, and a dead end circumferentialgroove 115. The axial bore groove 155 is desirably on one end of theseal segment 60 that is proximal to the segment's tongue 65. However,the present invention is not limited to this embodiment. The axial boregroove 155 may be substantially square or rounded with a depth withinthe range of 0.0005 to 0.035 inches wherein the depth is desirablybetween 0.20 to 0.025 inches in depth. The depth of the axial boregroove 155 may be dependent upon multiple factors including, but notlimited to, the engine application, shaft rotational speeds, desiredseal life and the like. The axial bore may also be aerodynamically orhydrodynamically tapered such that air flow generated by the rotation ofthe shaft is received by the axial bore groove 155. Extending from, andin fluid communication with the axial bore groove 155, is the dead endcircumferential groove 115. The dead end circumferential groove 155 maybe squared or rounded with a depth of 0.035 to 0.045 inches. To thisend, the transition between the axial bore groove 155 and the dead endcircumferential groove 115 may be a step-off from the depth of the boregroove 155 to the deeper circumferential groove 115 or a taper whereinthe transition from the depth of the axial bore groove 155 to thecircumferential groove 115 is gradual. However, the present invention isnot limited to these embodiments. Rather, in another embodiment, thedepths of the axial bore groove 155 and the circumferential groove 115are the same, within or between either of the depth ranges above.Optionally, a dam may also be provided between the axial bore groove 155and the dead end circumferential groove 115 wherein the darn may alsocontain an optional bleed hole in accordance with the dam structureabove.

Also extending perpendicularly from the axial bore groove 155, and alongthe longitudinal axis of the seal segment 60, is at least onelongitudinal bore groove 175. The longitudinal bore groove 175 may besemi-cylindrical in shape and extend along substantially the entirelength of the seal segment 60 toward the socket 70. Along a perimeterwall, of the longitudinal bore groove 175 is at least one hydrodynamicgroove 160. The pitch angle of the hydrodynamic groove is at an obliqueangle with respect to the longitudinal axis of the seal ring segment 60and is angled such that the hydrodynamic groove urges air flow receivedby the axial bore groove 155 along the longitudinal axis of the sealsegment 60. In one embodiment, the hydrodynamic groove may be of a depthrange of 0.0005 to 0.035 inches wherein the depth is desirably between0.20 to 0.025 inches. To this end, the circumference of the longitudinalbore groove 175 may be at least 0.0010 to 0.070 wherein thecircumference is desirably between 0.004-0.040 inches.

Proximal to the socket 70 end of the seal segment 60 is a pressurechamber 165. The pressure chamber 165 may be of a depth of 0.040-0.050inches and may be in fluid communication with the longitudinal boregroove 175. In one embodiment, a radial bleed hole 170 may extend fromthe pressure chamber 165 to the socket 70 such that the socket is influid communication with the pressure chamber 165.

In each of the above embodiments, the varying measurements may befurther tailored based on factors such as the speed of rotation of theshaft, pressure differential between the sump and the gas side of theseal, temperature, size of the rotatable shaft, or similar parameters tooptimize the efficiency of air movement and the pressure created with inthe dead end circumferential groove. To this end, the measurements ofeach of the above elements may be scaled up or down based upon the sizeof the fluid seal assembly and the aforementioned factors in tailoringthe measurements thereof. Accordingly, the ranges provided for each ofthe elements above are intended to limit the size of the presentinvention and the present invention may be scaled up or down inaccordance with parameters above.

In operation, as the shaft 40 rotates, air flow is generated around theshaft. The axial bore groove 155 directs the air flow to both the deadend circumferential groove 155 and the longitudinal bore groove 175.Within the longitudinal bore groove 175, air is directed by thehydrodynamic groove 160 along the longitudinal bore groove'slongitudinal axis toward and into the pressure chamber 165. Thehydrodynamic groove 160, therefore, functions to generate gas pressure,increasing along the longitudinal axis of the longitudinal bore groove175, due to the viscosity of the gas and shear forces on the molecules.To this end, pressurized gas is contained in the pressure chamber 165,which is vented into the socket 70 through the radial bleed hole 170. Byproviding a radial bleed hole 170 connected to the pressure chamber 165and, ultimately, the hydrodynamic groove 160, gas pressure continues toblow into the joints even at low or reverse pressure conditions. Thus,forcing pressurized air into the sockets acts as a seal within thesocket/tongue joints of two adjacent seal segments and prevents liquidweepage therethrough.

Additionally, because the axial bore groove 155 intersects directly withthe dead end circumferential groove 115, the dead end circumferentialgroove accumulates air resulting in an increase in pressure therein. Ifa bore dam is present between the axial bore groove and the dead endcircumferential groove, air pressure builds up at the axial boregroove/dam interface such that highly pressurized air is forced over thedam, or through an optional bleed hole, and into the dead endcircumferential groove 115. In either case, the pressure within the deadend groove 115 is redirected toward the shaft creating a lift force onthe seal segments wherein the lift force expands the sealing segmentsaway from the shaft creating a minute clearance between the shaft-faceof the seal segments and the rotating shaft. The redirection of thepressurized air within the dead end groove toward the shaft also createsan air/pressure seal within this minute clearance wherein the force ofthe high-pressure gas is at a sufficient velocity to prevent lubricantstored within the chamber from passing through the clearance. This airpressure seal is juxtaposed to the bore dam of the shaft-face of theseal such that the bore dam acts in concert with the air/seal to preventlubricant from escaping from the housing chamber during operation of theturbine engine. In other words, lubricant is prevented from escapingfrom the lubricant side to the gas side of the chamber. Thisconfiguration has the advantages of creating an air seal that does notinterfere with the rotation of the shaft, while reducing the wear on theshaft-side face seal as a result of the rotation of the shaft.

The third embodiment of the present invention containing thelongitudinal bore grooves has the same advantages as the firstembodiment. Specifically, the longitudinal bore grooves are advantageousbecause they greatly reduce leakage of liquids into the region on thegas side of the seal, regardless of the pressure differential across theface of the seal. In other words, the seal is able to function duringboth high and low air side to oil side pressure differential, as well aswhen negative pressure exists on the air side. Furthermore, thelongitudinal bore grooves generate less heat due to friction becausethere is minimal rubbing between the seal bore and the runner or theshaft. This provides extended seal wear life compared to a standardcircumferential seal contacting the runner. Finally, the longitudinalbore grooves is advantageous because it provides for reduced boreloading, thus, allowing for a more robust seal face.

Referring to FIG. 12, an alternative to the third embodiment of thepresent invention is illustrated. FIG. 12 illustrates an aspect of theinvention in which the axial bore groove 155 does not intersect the deadend circumferential groove 115. More specifically, in this embodimentthere are two longitudinal bore grooves each with a respectivehydrodynamic groove and pressure chamber. The first longitudinal boregroove 175, just as the above embodiment, extends from the axial boregroove 155 and contains a hydrodynamic groove 160 therein which directsair into a pressure chamber 165. The pressurized air of the pressurechamber 165 is vented into the socket 70 by the radial bleed hole 170.

The second longitudinal bore groove 185 also extends from the axial boregroove 155 along the longitudinal axis of the seal segment. The secondlongitudinal bore groove 185 is semi-cylindrical in shape and extendsalong substantially the entire length of the seal segment 60 toward thesocket 70 end of the seal segment. Along a perimeter wall, of the secondlongitudinal bore groove 185 is at least one hydrodynamic groove 190.The pitch angle of the hydrodynamic groove 190 is at an oblique anglewith respect to the longitudinal axis of the seal segment 60 and isangled such that the hydrodynamic groove 190 directs air from the axialbore groove 155 along the longitudinal axis of the seal segment 60. Inone embodiment, the shallow hydrodynamic groove may be of a depth rangeof 0.002-0.020 inches. To this end, the circumference of the secondlongitudinal bore groove 185 is at least 0.004-0.040 inches.

At the socket 70 end of the seal segment 60 is a second pressure chamber195. The pressure chamber 195 may be of a depth of 0.040-0.050 inchesand is in fluid communication with both the second longitudinal boregroove 185 and the dead end circumferential groove 115. In oneembodiment, the second pressure chamber 195 is separated from the deadend circumferential groove 115 by a bore dam (not illustrated), thusgenerating very high pressure. Specifically, air pressure builds up atthe pressure chamber/dam interface such that highly pressurized air isforced over the dam and into the dead end circumferential groove 115.

In operation, as a shaft rotates, air is generated around the shaftwhich enters both of the longitudinal bore grooves 175 and 185 by way ofthe deep axial bore groove 155. Within the first longitudinal boregroove 175, air is directed toward the pressure chamber 165 andultimately to the socket 70 by way of the radial bleed hole 170, asdescribed above. Within the second longitudinal bore groove 185, air isdirected by the hydrodynamic groove 190 along the longitudinal boregroove's longitudinal axis toward and into the second pressure chamber195. The hydrodynamic groove 190 of the second longitudinal bore groove1853 therefore, functions to generate gas pressure, which increasesalong the longitudinal axis of the longitudinal bore groove 185 due tothe viscosity of the gas and shear forces on the molecules. To this end,pressurized gas is contained in the second pressure chamber 195, whichmay then be vented into the dead end circumferential groove 115 andmaintain the seal between the shaft and seal segments in accordance withthe foregoing.

Referring to FIG. 13, another alternative to the third embodiment of thepresent invention is illustrated. Specifically, the axial bore 155 islocated at the socket 70 end of the seal segment and dimension inaccordance with the description above. One or more longitudinal boregrooves 200 extend from the axial bore 155 both along the longitudinalaxis of and toward the tongue 65 end of the seal segment. Thelongitudinal bore grooves 200 may be dimensioned in accordance with theabove and each contain at least one hydrodynamic groove 215 also inaccordance with the dimensions discussed above wherein the pitch anglesof each hydrodynamic groove 215 may be the same or at varying angles.Each of the longitudinal bore grooves 200 is in fluid communication witha single pressure chamber 205, as dimensioned above, wherein thepressure chamber 205 is at the tongue 65 end of the seal segment. Thepressure chamber 205 is in fluid communication with the dead endcircumferential groove 115 at an end of the groove proximal to thetongue 65 of the seal segment.

At the end of the dead end groove proximal to the socket 70, is a radialbleed hole 210. The radial bleed hole is in fluid communication with thedead end circumferential groove 115 and the socket 70 such thatpressured air within the dead end circumferential groove 115 may escapeinto the socket 70.

In operation, as a shaft rotates, air flow is generated around theshaft. The axial bore groove 155 directs air flow to each of thelongitudinal bore grooves 200. Within each the longitudinal bore groove200, air is directed by the hydrodynamic grooves 215 of each bore 200along the longitudinal axis of the seal segment and toward and into thepressure chamber 205. The shallow hydrodynamic grooves 215, therefore,function to generate gas pressure, increasing along the longitudinalaxis of each longitudinal bore groove 200, due to the viscosity of thegas and shear forces on the molecules. To this end, pressurized gas iscontained in the pressure chamber 205, which may then be vented into thedead end circumferential groove 115 and maintain the seal between theshaft and seal segments in accordance with the foregoing.

The pressurized air within the dead end circumferential groove 115 mayalso be vented into the socket 70 through the radial bleed hole 210. Byproviding a radial bleed hole 210 connected to the dead endcircumferential groove 115, gas pressure continues to blow into thesocket/tongue joints even at low or reverse pressure conditions. Thus,forcing pressurized air into the sockets acts as a seal within thesocket/tongue joints of two adjacent seal segments and prevents liquidweepage therethrough.

In an even further alternative third embodiment of the presentinvention, there may be more than one axial grooves on each sealsegment, as illustrated in FIG. 14. Specifically, one or more axial boregrooves 155 may be position along the length of the seal segment. In anon-limiting, example, as illustrated in FIG. 14, the seal segments maybe comprised of at least two axial bores. The first axial bore groove155 may be located at the socket 70 end of the seal segment anddimension in accordance with the description above. One or morelongitudinal bore grooves 225 extend from the axial bore groove 155 bothalong the longitudinal axis of and toward the tongue 65 end of the sealsegment. The longitudinal bore grooves 225 may be dimensioned inaccordance with the above and each contain at least one hydrodynamicgroove 250 also in accordance with the dimensions discussed abovewherein the pitch angles of each hydrodynamic groove 250 may be the sameor at varying angles. Each of the longitudinal bore grooves 225 is influid communication with a pressure chamber 220, as dimensioned above,wherein the pressure chamber 220, in a non-limiting embodiment, may besubstantially centered on the seal segment. The pressure chamber 220 isin fluid communication with the dead end circumferential groove 115.Adjacent to the pressure chamber 220 is a second axial bore groove 235.The second axial bore groove 235, in a non-limiting embodiment, may belocated substantially centered on the seal segment and dimension inaccordance with the above. One or more longitudinal bore grooves 240extend from the second axial bore groove 235 both along the longitudinalaxis of and toward the tongue 65 end of the seal segment. Thelongitudinal bore grooves 235 may be dimensioned in accordance with theabove and each contain at least one hydrodynamic groove 255 also inaccordance with the dimensions discussed above wherein the pitch anglesof each hydrodynamic groove 255 may be the same or at varying angles.Each of the longitudinal bore grooves 240 is in fluid communication witha second pressure chamber 230, as dimensioned above, wherein the secondpressure chamber 230 is at the tongue 65 end of the seal segment. Thesecond pressure chamber 230 is in fluid communication with the dead endcircumferential groove 115. To this end, both the first and secondpressure chambers 220, 230 are both in communication with the dead endcircumferential groove 115.

At an end of the dead end groove proximal to the socket 70, is a radialbleed hole 245. The radial bleed hole is in fluid communication with thedead end circumferential groove 115 and the socket 70 such thatpressured air within the dead end circumferential groove 115 may escapeinto the socket 70.

In operation, as a shaft rotates, air is generated around the shaftwhich enters each of the longitudinal bore grooves 225, 240 by way ofthe each bore's respective deep axial bore groove 155, 235. Within eachthe longitudinal bore groove 225, 240, air is directed by thehydrodynamic grooves 250, 255 along the longitudinal axis of the sealsegment toward and into each respective pressure chamber 220, 230. Thehydrodynamic grooves, therefore, function to generate gas pressure,increasing along the longitudinal axis of each longitudinal bore groove225, 240, due to the viscosity of the gas and shear forces on themolecules. To this end, pressurized gas is contained in both pressurechambers 220, 230. Because both pressure chambers 220, 230 are in fluidcommunication with the dead end circumferential groove 115, thepressurized gas may then be vented into the dead end circumferentialgroove 115 and maintain the seal between the shaft and seal segments inaccordance with the foregoing.

The pressurized air within the dead end circumferential groove 115 mayalso be vented into the socket 70 through the radial bleed hole 245. Byproviding a radial bleed hole 245 connected to the dead endcircumferential groove 115, gas pressure continues to blow into thesocket/tongue joints even at low or reverse pressure conditions. Thus,forcing pressurized air into the sockets acts as a seal within thesocket/tongue joints of two adjacent seal segments and prevents liquidweepage therethrough. Because pressure is generated regardless of thespeed of the rotating shaft, pressure continues to blow into the jointsand between the seal segments and the shaft even at low or reversepressure conditions.

What is claimed is:
 1. A method of sealing a liquid region from a gasregion across an annular surface of a rotating shaft utilizing aplurality of adjoining annularly sealing ring segments facing therotating shaft, each sealing ring segment having a dead endcircumferential groove formed within a shaft-side face of each sealingring segment at a position closer to the liquid region than to the gasregion such that, when the sealing ring segments are positionedproximate the annular surface, the dead end circumferential groove ofeach sealing ring segment extends arcuately in direction of shaftrotation, and at least two additional grooves each consisting of ahydrodynamic shallow pocket along the shaft-side face of each sealingring segment wherein each additional groove is in fluid communicationwith the dead end circumferential groove, each hydrodynamic shallowpocket having a pocket, an inlet extending from the pocket away from thedead end circumferential groove, an outlet, and a dam extending betweenthe pocket and the outlet with a bleed slot passing through the dam, theoutlet extending toward the dead end circumferential groove wherein thehydrodynamic shallow pocket, by way of the bleed slot and the outlet, isin fluid communication with the dead end circumferential groovecomprising the steps of: urging the sealing ring segments toward therotating shaft such that the sealing ring segments form a seal with therotating shaft when the rotating shaft is not rotating; rotating therotating shaft; directing fluid flow generated by the rotating shaftalong each additional groove and into the dead end circumferentialgroove such that a fluid is pressured as it flows along each additionalgroove and into the dead end circumferential groove; redirecting thefluid within the dead end circumferential groove toward the rotatingshaft so as to provide a lift force on the sealing ring segments thatlifts the sealing ring segments away from the rotating shaft; andcreating an air seal around the rotating shaft as the pressurized airwithin the dead end circumferential groove is urged toward the rotatingshaft, thereby, maintaining sealing between the rotating shaft and thesealing ring segments during rotation and non-rotation of the rotatingshaft.
 2. The method of claim 1, further comprising the step of:directing a portion of the fluid within the dead end circumferentialgroove into a second bleed slot between one said dead endcircumferential groove and a socket at a joint between adjoining sealring segments.
 3. A seal assembly for sealing a liquid region from a gasregion across an annular surface of a rotating shaft comprising: aplurality of adjoining annularly sealing ring segments facing therotating shaft wherein each sealing ring segment includes a dead endcircumferential groove within a shaft-side face of each sealing ringsegment such that, when the sealing ring segments are joined about theannular surface, the dead end circumferential groove of each sealingring segment extends arcuately in direction of shaft rotation; and atleast two additional grooves extending across the shaft-side face ofeach sealing ring segment leading to the dead end circumferential groovewherein each additional groove is in fluid communication with the deadend circumferential groove and directs fluid into the dead endcircumferential groove; each additional groove is comprised of ahydrodynamic shallow pocket having a pocket, an inlet extending from thepocket away from the dead end circumferential groove, an outlet, and adam extending between the pocket and the outlet with a bleed slotpassing through the dam, the outlet extending toward the dead endcircumferential groove wherein the hydrodynamic shallow pocket, by wayof the bleed slot and the outlet, is in fluid communication with thedead end circumferential groove so as to direct fluid flow generatedfrom rotation of the rotating shaft into the dead end circumferentialgroove.
 4. The assembly of claim 3, wherein the pocket, the inlet, andthe outlet are of uniform and constant depth.
 5. The assembly of claim3, wherein the pocket, the inlet, and the outlet are each of variabledepths.
 6. The assembly of claim 3, wherein the pockets are deeperproximate the inlet than at the outlet.
 7. The assembly of claim 3,wherein the inlet and the outlet grooves are inclined and in concertwith direction of rotation of the rotating shaft.
 8. The assembly ofclaim 3, further comprising: a second bleed slot between one said deadend circumferential groove and a socket along a joint between adjoiningsealing ring segments.
 9. The assembly of claim 3, wherein the pocket,the inlet, and the outlet are each of constant width.
 10. The assemblyof claim 3, wherein the pocket, the inlet, and the outlet are each ofvariable width.
 11. A seal assembly for sealing a liquid region from agas region across an annular surface of a rotating shaft comprising: aplurality of adjoining annularly sealing ring segments facing therotating shaft wherein each sealing ring segment includes a dead endcircumferential groove within a shaft-side face of each sealing ringsegment such that, when the sealing ring segments are joined about theannular surface, the dead end circumferential groove of each sealingring segment extends arcuately in direction of shaft rotation; and atleast two additional grooves extending across the shaft-side face ofeach sealing ring segment leading to the dead end circumferential groovewherein each additional groove is in fluid communication with the deadend circumferential groove and directs fluid into the dead endcircumferential groove, each additional groove is comprised of ahydrodynamic pocket having a shallow pocket, an inlet extending from theshallow pocket away from the dead end circumferential groove, an outlet,and a dam extending between the shallow pocket and the outlet with ableed slot passing through the dam, the outlet extending toward the deadend circumferential groove wherein the hydrodynamic pocket, by way ofthe bleed slot and the outlet, is in fluid communication with the deadend circumferential groove so as to direct fluid flow generated from therotating shaft into the dead end circumferential groove.
 12. Theassembly of claim 11, further comprising: a second bleed slot betweenone said dead end circumferential groove and a socket along a jointbetween adjoining sealing ring segments.
 13. The assembly of claim 11,wherein the shallow pocket, the inlet, and the outlet are each ofconstant width.
 14. The assembly of claim 11, wherein the shallowpocket, the inlet, and the outlet are each of variable width.
 15. Theassembly of claim 11, wherein the shallow pocket, the inlet, and theoutlet are each of constant depth.
 16. The assembly of claim 11, whereinthe shallow pocket, the inlet, and the outlet are each of variabledepth.
 17. The assembly of claim 11, wherein the shallow pockets aredeeper proximate the inlet than at the outlet.
 18. The assembly of claim11, wherein the inlet and the outlet grooves are inclined and in concertwith rotational direction of the rotating shaft.